1. Field of the Invention:
The present invention relates to a flyback transformer, and more particularly to a flyback power supply which applies a high voltage to the anode of a cathode-ray tube for use in a television receiver, a cathode-ray tube display, or the like.
2. Prior art:
Cathode-ray tubes (CRTs) used in television receivers and display terminals require a very high anode voltage in their operation. These television receivers and display terminals are equipped with flyback power supplies for boosting and rectifying flyback pulses to produce such a very high anode voltage.
Recent color television receivers with CRTs are required to be compatible with various pieces of audio and video equipment, to receive multiplex broadcasts such as character display programs, and to have larger screens. Display terminals with CRTs are also required to have larger screens and higher image resolution. To meet these requirements, flyback transformers or power supplies used with those CRTs should produce a high output voltage and a high output current and have as small high-voltage fluctuations, ringing, and undesired radiation as possible. The flyback power supplies should also be inexpensive so that they can be employed in general-purpose television receivers.
Conventional flyback transformers include a high-voltage coil composed of successive coil layers. Since the high-voltage coil has a large diameter, its outer coil layers are less magnetically coupled to the low-voltage coil, resulting in an increase in their leakage inductance and a reduction in their resonant frequency. The conventional flyback transformers have therefore been poor in high-voltage regulation.
Japanese Laid-Open Utility Model Publications Nos. 62(1987)-104416 and 62(1987)-104417 disclose flyback transformers with improved regulation. The disclosed flyback transformers include two high-voltage coil units mounted on a single core leg. These flyback transformers are however relatively long and their core legs are also long. The long flyback transformers cannot easily be mounted in place in television receivers and display terminals since modern television receivers and display terminals employ relatively small casings. The long core legs are also disadvantageous in that they tend to warp and have reduced mechanical strength, and are costly to manufacture.